Polyamides

ABSTRACT

Deep dye polyamides prepared from thermally stable polymers, e.g., 6 or 6.8 nylon, using excess base stabilizer in the presence of a chain branching agent.

United States Patent Middleton Aug. 29, 1972 [54] POLYAMIDES [56] References Cited [7 2] Inventor: Ronald David Middleton, Pontypool, UNITED STATES PATENTS England 2,863,857 12/1958 Costain et a]. ..260/78 TE [73] Assignee; Imperial Chemical Industries 2,989,798 6/1961 Bannerman ..260/78 SC Limited, 3 Millbank, England 3,304,289 2/1967 Ballentine et a1. .....260/78 TF 3,437,641 4 1 6 -1 22 Filed: Dec. 4, 1970 9 9 ct 260/78 L [2] 1 App]. No: 95327 OTHER PUBLICATIONS Man Made Fibers, Mark et al., Vol. 2, 1968, p. 218. Relawd 15- Application Data Synthetic Heterochain Polyamides, Korshak et al., [63] Continuation of Set. NO. 726,219, May 2, 1964 1968 abandoned' Primary Examiner-Harold D. Anderson 52 us. 01 ..260/78 R, 8/178 R, 57/140 R, and Stephen Murphy 260/78 A, 260/78 L, 260/78 TF TR 51 110.01. ..C08g 20/20 [57] ABS CT [58] Field 61 Search ..260/78 A, 78 L, 78 TF p y polyarmdes P p from therrmllly Stable polymers, e.g., 6 or 6.8 nylon, using excess base stabilizer in the presence of a chain branching agent.

5 Claims, No Drawings POLYAMIDES The present invention, which is a continuation of application Ser. No. 726,219, filed May 2, 1968, now abandoned, relates to modified polyamides and is especially concerned with the modification of polyamides having a gel time in excess of 1,500 minutes to yield polymers which may be melt spun into filaments having enhanced affinity for anionic dyestuffs.

The requirement for modified polyamide yarns which have deep dye or ultra deep dye characteristics, that is yarns which will take up relatively large amounts of anionic dyestuffs and hence dye to a deeper shade than yarns spun from standard polymer, has long been recognized and considerable work involving the use of additives, or the preparation of copolymers containing a major proportion of the unmodified polyamide, has been undertaken in order to achieve this result.

One technique is to produce a modified polymer having a large number of amine end groups available which will substantially increase the affinity of the fibers produced therefrom for anionic dyestufis. The availability of amine end groups may be achieved by the use of an excess of base during the polymerization of polyamide, however, such polyamides have only low melt and relative viscosities and consequently have poor spinning performance. The minimum melt viscosity for melt spinning is considered to be 400 poises at 25 C above the optical melting point of the polymer.

It is also known that the melt and relative viscosity of a polyamide may be raised by the incorporation of a branching agent during the polymerization process.

Attempts to produce a deep dye polyamide yarn from polyhexamethylene adipamide produced by the polymerization of hexamethylene diammonium adipate in the presence of an excess of base and with the addition of sufficient branching agent to effect a significant increase in melt viscosity of the polymer have been unsuccessful since polymers produced in this way rapidly gel and melt spinning is impracticable.

We have now found that the modified polyamide yarn having enhanced affinity for anionic dyestuffs may be obtained by melt spinning polymer prepared by the polymerization of a lactam, an alpha-omega-amino acid or a salt of a diamine and di-carboxylic acid or functional equivalents thereof and having a gel time in excess of 1,500 minutes in the unmodified condition in the presence of excess base and a chain branching agent.

Accordingly, therefore, the present invention provides a modified polyamide having a melt viscosity of at least 400 poises at a temperature of 25 C above the optical melting point of the polymer, derived from a lactam, an alpha-omega-amino carboxylic acid or the salt of a diamine and di-carboxylic acid or functional equivalents thereof polymerized in the presence of excess base and a chain branching agent, the polymerization of the lactam, alpha-omega-amino carboxylic acid or salt yielding an unmodified polyamide having the gel time of at least 1,500 minutes.

Suitable polyamides include:

polyepsilon caprolactam polyhexamethylene suberamide polyhexamethylene sebacamide polyaminoundecanoic acid.

Copolymers of polyhexamethylene adipamide and polyepsilon caprolactam in the proportions /25 to 25/75 parts by weight are also suitable.

As chain branching agents there may be mentioned bis-hexamethylene triamine and timesic acid.

By the term excess base we mean the amount of base added in excess of that required to be equivalent to the number of carboxyl groups present for polymerization, the excess being sufiicient, after allowing for any loss of base during polymerization, to give an excess of basic over acidic end groups high enough to yield a polymer which can be spun into filaments exhibiting deep-dye characteristics.

The amount of chain branching agent required is determined empirically and is the amount necessary to raise the melt viscosity, and therefore also the relative viscosity, of the polyamide, polymerized in the presence of excess base, to a level suitable for commercial melt spinning. Thus the melt viscosity should be at least 400 poises measured at 25 C above the optical melting point of the polymer.

Generally the concentration of chain branching agent should be in the range 20-150 moles per 10 grams of salt or lactam, preferably 60-100 moles per 10 grams of salt or lactam.

The excess base and chain branching agent may be one and the same substance, for example bis-hexamethylene triamine. However, in this instance, if a sufficient quantity of the chain branching agent/base is added to provide an adequate number of branch points to effect a useful increase in melt viscosity, then the number of basic groups also added will result in the polymer having a reduced molecular weight owing to the reversal of the polyamidation. The addition of a small amount of a dibasic acid to counteract the presence of the very large number of basic groups effectively raises the melt viscosity to the required level whilst leaving the excess of basic over acidic end groups sufficiently high for the polymer to have the desired dyeing characteristics.

In order that the modified polyamide should have the desired deep dyed characteristics the polymer should have an excess of basic over acidic end groups (A C) of at least and preferably between and 200. The proportions of excess base, chain branching agent and di-acid (where required) should be arranged to meet this requirement but still provide a polymer as defined above.

The invention also provides a process for the manufacture of a modified polyamide having a melt viscosity of at least 400 poises measured at a temperature of 25 C above the optical melting point of the polymer, by the polymerization of a lactam, an alpha-omega amino carboxylic acid or the salt of a dicarboxylic acid or diamine or functional equivalent thereof which yield an unmodified polyamide having a gel time of at least 1,500 minutes, wherein the polymerization is carried out in the presence of excess base and a chain branching agent.

The gel time of a polymer is measured using a modified form of Tecam gelation timer made by Techne Limited of Cambridge. In the timer a rod of weight 20.5 g., diameter one-eighth inch and approximate length 13 inches, is connected by a link with end play in it to a crank turned by a synchronous motor.

The rod falls under gravity into a cylindrical aluminum tube of %inch internal diameter, and is so positioned that it reaches to within one-half inch of the base of the cylinder on completion of the down stroke. The rod is pulled up on the up stroke by the synchronous motor. A sample of polymer, weight 10.5 g. is contained in the cylindrical tube maintained at 25 C above the optical melting point of the polymer by a suitable heating device and a current of steam passed over the surface of the polymer to prevent oxidation. At gel point the rigidity of the polymer is sufficient to support the weight of the rod and this causes an electric circuit to be closed which switches off a timing mechanism thus recording the gel time.

The melt viscosity of a polymer is determined using a melt viscometer comprising a stainless steel tube of approximately cm. length and 1 cm. internal diameter. This tube is closed at one end by the insertion of a spinneret containing in the center a circular orifice of known length and radius. The melt viscosity is then determined by placing about 2 grams of the polymer in the tube and inserting a small stainless steel ball having a diameter slightly less than the internal diameter of the tube on top of the polymer. Nitrogen is blown through the tube to expel oxygen and the tube placed inside a heater maintained at the temperature required for the determination. The tube is allowed to remain in the heater for minutes to ensure complete melting of the polymer after which nitrogen, at 100 p.s.i.g. is supplied to the top of the tube to force polymer through the orifice. After a uniform flow of polymer has been established the threadline is cut and the weight of polymer extruded in a finite time determined. The melt viscosity is calculated from the Poiseuille equation appearing at page 220 of General Properties of Matter by Newman and Searle.

The present invention further includes filaments and fibers spun from the above-mentioned polymer, preferably by melt spinning techniques, which filaments dye to a deeper shade than filaments spun from unmodified polymer when using acid dyestuffs.

Yarns containing filaments as defined above may be crimped, for example by the well-known stuffer box technique, and are especially useful in pile fabrics, such as carpets, when used together with a standard yarn to give two-tone color effects.

The following examples illustrate but do not limit the invention.

EXAMPLE 1 Six thousand g. of hexamethylene diammonium suberate, 48 g. of hexamethylene diamine and 33.4 g. of bis-hexamethylene triamine were placed together in an autoclave and polymerization effected in the usual manner. The resultant polyhexamethylene suberamide (6.8 nylon) had the following properties:

Relative viscosity 29 Melt viscosity at C 465 poise Amine end group content g/lO g. (A) 183 Carboxyl end group content g/lO g. (C)

A C 163 Gel time 1500 mins. Gel time for unmodified 6.8 nylon 6000 mins.

The polymer was melt spun into filaments which were drawn to orient them using standard equipment.

The resultant yarn had much improved affinity for acid dyestuffs.

The effect of the chain branching agent in increasing the A C value for a given value of relative viscosity or of increasing the relative viscosity for a given value of A C may be illustrated as follows using polyhexamethylene suberamide as a model:

The relationship between RV. and total end group (T.E.G.) content, i.e., the sum total of end groups as determined by titration, for 6.8 nylon in the RV. range 1645, may be expressed according to the following formula:

log RV. 5.190 1.683 log T.E.G.

Thus for a polymer of RV. 29 the total end group value should be 164.

The equilibrium constant for this polymerization is such that under 1 atmosphere of steam at 290 C the product A X C is equal to 2,440.

Thus

Solution of these equations shows that A 147.5, C 16.5 and therefore that A C 131. This figure is significantly lower than the value of 163 obtained in the Example.

The RV. of the polymer having A (#163 obtained using excess base stabilizer only can also be calculated. In this case the equations would be:

AXC=2,440

Solution of these equations shows that A 177 and C l4, T.E.G. is thus 191 and the above-mentioned empirical relationship shows this to correspond to an RV. of only 22.5, which is too low for melt spinning processes.

The relative viscosity (R.V.) referred to above is the viscosity of an 8.4 percent w/w solution of polymer in percent aqueous formic acid relative to the viscosity of the formic acid.

EXAMPLES 2 TO 6 Samples of polyepsilon caprolactam containing varying concentrations of bis-hexamethylene triamine (HMT) and sebasic acid were prepared by Carius tube polymerizations. Reactants were heated, together with 15 percent of water as a polymerization catalyst, in a sealed Carius tube for 2% hours at 260 C and a further 1% hours at 280 C under an atmosphere of steam and atmospheric pressure. Details of the additive concentrations and polymer properties are given in Table 1.

5 6 3 22 nil 30.9 121 39 82 l600 Pobis Sebg/l"g g/lOg Visc- MN. 4 89 89 181.0 147 34 H3 4000 ly HMTacic osity meas- 5 s9 44 27.9 220 24 196 625 Ex. mer a id poise 6 s9 22 24.1 242 22 220 400 mam I n a n e s 5 To obtam a suitable melt v1scos1ty for melt spinning, "01 75/25 nil n11 s9 47 22 when using HMT as the excess base and the chain H 89 44 25 m 900 270 branching agent, the concentration of HMT had to be Con reduced to 22 moles per grams of polyepsilon 22 61 56 5 650250 caprolactam at which point the excess of amine end 10 60 n" 90 24 66 2865 groups over acid end groups (A C) value was only 13 a9 44 191 28 I63 400 just sufficient to impart a deep dye characteristic to the polymer. The addition of sebacic acid enabled increased amounts of HMT to be added to give the Although polyhexamethylene adipamide containing preferred -C value and a me vlSCOSlty d q for 15 HMT and an excess base cannot be successfully melt melt spmmngspun because of the tendency of the polymer to gel, the

Yam p from the p f havmg A f Values addition of as little as 25 percent polyepsilon caprolacabove 80 all showed deep dyeing charactensucs when tam permits l spinning. Yams Spun f m the y wlth acld dyestuffspolymers containing HMT all have deep dyeing charac- EXAMPLES 8 TO 10 Samples of hexamethylene sebacamide and EXAMPLE 14 polyammo-undecanoic ac1d were prepared by Camus Caprolactam and hexamethylene diammonium tube polymenzations 1n which the reactants were adipate, in proportions to yield a 5050 Weight f heated 1n a sealed tube for 3 hours at 220 C and then weight copolymer, together with bis hexamethylene for a further 1% hours at atmoosphenc Pressure f triamine, sebacic and water were polymerized in an auatmosphere steam at 280 Detafls of f' toclave according to the normal procedure for 6.6 concentratlons and Polymer propemes are glven nylon. The additive concentrations and polymer pro- Table perties are shown in Table 4.

TABLE 2 TABLE 4 Additives Polymer Properties (moles/ 10 Temp- Polymer properties Temp pm 11: 'Zg' g' gsalt) 11.1). A.E.G. 0.15.0. A-C Melt for E ;g my "was. r g- '3 222- B/lo'g s/m X'mer polse :2; Ex. mer acid poise "pars;

Ion s 89 44 220 22 198 3990 7 60 nil 229 I6 213 677 Conll trol ny lon nil nil so 37 13 4o0- EXAMPLE 15 10 89 44 206 21 185 866 270 45 9 60 213 12 603 Ammo undecanoic acid and bis-hexamethylene triamine together with sebacic acid were polymerized I in an autoclave according to the procedure described addlflon 0f $ebaclc Q f to desll'able to in Example 14. Details of the additive concentrations glve Polymers having a deslred high amme C and 5 and polymer properties are given in Table 5. adequate melt viscosities, although the addltlon of the sebacic acid is clearly not essential. Yarns spun from TABLE 5 the polymers containmg HMT all show deep dyeing Additives polymerpmpemes charactenstics. (moles/10a Temp gsalt) R.U. A.E.G. C.F.G. AC Melt for EXAMPLES 11 to 13 Pobis Sebg/lO'g g/lOg Visc- M.V. ly- HM'ficid osity meas- Copolymers of polyepsilon caprolactam and met acid Poise polyhexamethylene adipamide in proportions 75/25 and 25/75 parts by weight were prepared by Carius tube polymerizations in the manner described in Exam- 3 89 44 209 ples 2-6 omitting the addition of water. Concentration of additives and polymer properties are given in Table Although the above examples all relate to the use of A E 3 aehain branching agent which is itself a base, notably H bls-hexamethylene tr1am1ne, it is also permissible to assay Pdyme' Pmpemes Temp employ chain branching agents which are acidic in nag/ Sail) 11.5.0. 0.12.0. A-C Melt for ture. Clearly when using such chain branching agents,

it may be necessary to add larger excesses of base to counteract the presence of the acid.

EXAMPLE 6 Caprolactam, trimesic acid and hexamethylene diamine were placed in a sealed Carius tube and heated at 260 C for 21 hours. At the end of this time the tube was opened and the contents heated under steam under atmospheric pressure at 280 C for a further 1% hours. 1

Details of the additive concentrations and polymer properties are given in Table 6.

TABLE 6 Additives Polymer properties (moles/l Temp. g salt) R.U. A.E.G. C.F.G. A-C Melt for Po- Tr- Hexag/l0g g/l0 g Visc- M.U. lyime-methosity meas- Ex. mer sic ylene poise ureacid diamine ment Yarns spun from this polymer exhibited deep-dye characteristics when dyed with acid dyestuffs.

Having thus disclosed the invention, what is claimed 1. A modified, fiber formable, deep dyeable, melt spinnable aliphatic polyamide, having a melt viscosity of at least 400 poises at 25 centigrade above the optica] melting point of the polymer, said polyamide consisting essentially of the polymeric condensation product, of a composition of (A) a monomer selected from the group consisting of a lactam, an alpha-omega aminocarboxylic acid, the salt of a diamine and an organic dicarboxylic acid and mixtures thereof, (B) excess bis-hexamethylene triamine and (C) 20-150 moles per 10 grams of (A) of a chain-branching agent selected from the class consisting of bis-hexamethylene 0 triamine and trimesic acid, the unmodified polyamide having a gel timeof at least 1,500 minutes, said modified polyamide having an excess of at least amino over carboxyl end groups.

2. Polyamide according to claim 1 wherein the chainbranching agent is bis-hexamethylene triamine and sebacic acid is included in the polymerization system in 

2. Polyamide according to claim 1 wherein the chain-branching agent is bis-hexamethylene triamine and sebacic acid is included in the polymerization system in amounts sufficient to increase the melt viscosity of the modified polyamide.
 3. The modified polyamide according to claim 1 wherein said polymer is selected from the group consisting of poly-epsilon-caprolactam, polyhexamethylene suberamide, polyhexamethylene sebacamide, and polyamino-undecanOic acid.
 4. A modified polyamide according to claim 1 wherein the polymer is selected from the class consisting of co-polymers of hexamethylene diammonium adipate and epsilon-caprolactam in proportions of 75/25 to 25/75 parts by weight.
 5. Filament or fiber of the polyamide of claim
 1. 